This invention relates to a tool for measuring Z-notch positions in a turbine bucket airfoil shroud.
Bucket airfoils twist and are often damaged by foreign object impact during operation. The Z-form profiles of bucket shrouds cannot therefore be measured relative to the original airfoil datum location points since these cannot be relied on to be in the original design specification position. Failure to control Z-form positions can result in uneven gaps between adjacent buckets such that when they reach temperature, they will bind and exert high axial stress on the bucket airfoils with the risk of catastrophic failure.
Crude gauges using a cookie cutter principle have been tried, but these devices did not provide accurate measurement of the bucket shroud position relative to design specifications. Rather, they were simple comparators that helped determine whether the profile of the shroud was correct.